Boiler pilot light won't stay on (Gloworm Swiftflow 80)

10 Oct 2012
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United Kingdom
I have an obsolete boiler (Gloworm Swiftflow 80) that has been running OK until recently, when the pilot light wouldn't stay on any more. I can push the valve button in, press the piezo button to ignite it, but then no matter how long I wait, the flame goes out as soon as I turn the valve and let it go.

I have a friend who is a plumber and Gas Safe qualified, and he's been trying to help me. I'm skint and can't afford to have a new boiler installed. I don't qualify for the boiler replacement scheme either, so my only option for now is to get this boiler running again, even though I know it's throwing good money after bad.

Now obviously the first thing he tried was fitting a new thermocouple. No joy, so he suggested getting a new gas valve (it's the SIT type for this one). I managed to get hold of one, he fitted it and sadly it's still not staying on.

Is there anything else that could be making it refuse to stay on? It's a problem that developed overnight, i.e. it had worked fine the day before this started happening.
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If the gas valve and the TC are new then the only thing left is the Overheat interrupter. Have your RGI check that.
Amazing how some RGIs don't know how to make the required voltage measurements on these to diagnose the problems.

Most unlikely the gas valve was at fault. You have demonstrated that.

Sorry your friend seems so unable to diagnose boiler faults. Just as well you are not paying him!

Pablo: Thanks. :)

Agile: Ha, I'm going to show him your post. :LOL:

He's a gas fitter working for a firm that installs and services modern boilers on large contracts for councils etc. I think this model is before his time, in all honesty. He even called up the manufacturers about it and they seemed to think if it wasn't the thermocouple then the valve must be at fault too.

Anyway, I'll give an update when this boiler is next looked at, which may be a few days from now.

If the overheat interrupter is fine (and he may well have already checked that, Agile, the guy isn't an idiot, obviously I don't know everything he may or may not have tried), is there anything else that could possibly be causing it?
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He is obviously an installer and working on council contracts which I think of as being the bottom end of the market. They work very hard and fast and its totally brain dead!

To be gas registered you are tested on gas valves and thermocouples but interrupter thermostats are hardly mentioned. There is no normal training which covers them.

Only those who do a lot of repairs are likely to have much experience of pilot light boilers unless they were working during the 70s and 80s before they were phased out because of their inefficiency.

Even of those above my experience indicates that barely 10% of RGIs who do repairs are familiar with the electronic testing which is required to properly diagnose those faults. In any case repairing a pilot light boiler is getting quite rare as they are few left now.

On line help people primarily just read the manuals out which do not explain what is needed. They would earn twice as much if they could do boiler repairs! An advert by Baxi Potterton in Warwick said "no experience necessary".

I have a big advantage in this respect because my background is in electronics with BBC Engineering.


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